1. Field of the Invention
The present invention relates to adjustable wheelchairs and, more particularly, to wheelchairs having an angularly adjustable backrest and seat.
2. Description of Related Art
Reclinable wheelchairs have evolved in accordance with special needs of patients as well as improving comfort and convenience of use. Exemplary prior art mechanisms for tilting backrests are shown in U.S. Pat. No. 3,815,586. Here, pivot bars extend from opposing armrests into the side edges of the backrest. A multi-orificed side plate allows for repositioning of the pivot bars and adjustment of the backrest tilt angle. The wheelchair seat is pivoted at its back edge and the front edge may be adjustably lifted with a toothed rack and pin device.
A problem with the above is the numerous individual adjustments that must be made for each movement. Also, the mechanisms are bulky and add weight to the overall chair. Further, the chair is not readily collapsible because the backrest and seat must be stiff and self-sustaining.
In G.B. Patent Application 2029334, a subassembly of arm, seat and foot rests all tilt together relative to the wheelchair frame. The pivot axis is at the seat and back junction. This arrangement entirely lacks versatility. It also involves the use of two separate structural frame assemblies which about doubles the weight.
G.B. Patent Applications 2136742, 2158350 and 2171898 provide wheelchair mechanisms whereby reclining the backrest causes a corresponding forward movement of the seat. This maintains a lowered center of gravity for the wheelchair occupant and a more stable wheelchair disposition. However, it is unnecessary to always combine seat movement with backrest tilting. Particularly with severely handicapped patients, it is better to have the backrest separately adjustable. Such also lessens the bulk and complexity of the wheelchair mechanisms and greatly facilitates collapsibility.